Field of the Invention
This invention relates to an improved composition and process for coating metal surfaces and more particularly to improved chromate conversion coatings for coating aluminum and aluminum alloy surfaces to provide improved corrosion resistant and paint bonding coatings on such surfaces. More particularly, the invention relates to aqueous acidic solutions which contain hexavalent chromium ions and fluoride ions which are improved by modifying the composition so as to provide a non-cracking corrosion resistant chromate coating on aluminum or aluminum alloy surfaces.